1. Field of the Invention
The present invention relates to a substrate processing apparatus for performing a series of processes upon substrates including a semiconductor substrate, a glass substrate for a liquid crystal display device, a glass substrate for a photomask, a substrate for an optical disc, and the like. More particularly, the present invention relates to an improvement in a controller for controlling the start timing of a thermal process of substrates subjected to an exposure process.
2. Description of the Background Art
With demands for higher density and higher degree of integration in the recent manufacture of semiconductor wafers, a technique has been required for size reduction of circuit patterns to be formed on the semiconductor wafers. To meet the requirement in the process steps of manufacturing semiconductor wafers, there has been proposed a technique which uses a chemically amplified resist as a photoresist to perform an exposure process, a thermal process and a development process on substrates coated with the chemically amplified resist, thereby to form patterns of a resist film on the substrates.
In the process of forming patterns in the resist film by using the chemically amplified resist, the exposure process is initially performed to direct light onto the resist film formed using the chemically amplified resist. This creates an acid catalyst in portions of the resist film exposed to the light, whereby patterns having a three-dimensional distribution are latent in the resist film. Next, when a heating process is performed on the substrates subjected to the exposure process, a chemical reaction which will cause a change in the rate of dissolution in a developing solution is activated by the catalytic action of the acid catalyst created in the exposed portions. Then, the chemical reaction substantially stops when a cooling process is performed on the substrates. The patterns of the resist film emerge onto the substrates when the development process is performed on the substrates.
However, in the above-mentioned process of forming the patterns in the resist film, the chemical reaction which will cause a change in the rate of dissolution in the developing solution is caused to proceed by the acid catalyst created in the resist film during a time interval between the completion of the exposure process and the start of the heating process.
For example, if variations in the length of time required to transport the substrates from an exposure part for performing the exposure process to a heating part for performing the heating process give rise to variations between the substrates in the length of time (also referred to hereinafter as “post-exposure delay time”) from the completion of the exposure process to the start of the heating process, there arise variations in the amount of acid catalyst created in the resist film prior to the start of the heating process.
Thus, the conventional technique fails to bring the dimensional accuracy of line widths and the like of the patterns formed in the resist film within a predetermined range. This presents a problem such that the dimensional accuracy of interconnect patterns formed on the substrates is not within a predetermined range.